Comparing the Performance of the Cary 3500 and Cary 8454 UV-Vis Spectrophotometers

Importance of the Topic

UV-Vis spectrophotometry remains a foundational analytical tool in pharmaceutical, academic, and industrial laboratories. Reliable quantification of key compounds such as potassium dichromate under Good Manufacturing Practice (GMP) conditions ensures method transferability, data comparability, and regulatory compliance. Advances in instrument design aim to enhance throughput, accuracy, and ease of use while preserving measurement integrity.

Objectives and Study Overview

This technical comparison evaluates the performance equivalence and practical advantages of two Agilent UV-Vis instruments: the diode array Cary 8454 (introduced in the 1980s) and the monochromator-based Cary 3500 (introduced in 2018). A well-established method for determining potassium dichromate concentration in 0.001 M perchloric acid was transferred from the Cary 8454 to the Cary 3500. Key objectives included:

• Confirming absorbance peak positions by wavelength scanning.
• Comparing calibration linearity and accuracy at 257 nm.
• Assessing photometric range and sample throughput.
• Measuring elapsed times for spectral scans and calibration routines.

Methodology and Instrumentation Used

Both instruments measured a blank (0.001 M perchloric acid), six calibration standards (40–240 mg/L potassium dichromate), and a 60 mg/L sample. Parameters:

• Wavelength scan: 190–600 nm displayed (Cary 8454) vs. 190–1100 nm (Cary 3500), 1 nm interval.
• Quantification: fixed wavelength at 257 nm, linear calibration, 3 s integration/averaging for Cary 8454; 3 s for Cary 3500.
• Signal averaging: 0.1 s for both; an additional Cary 3500 measurement used 0.004 s averaging.

Instrumentation:

• Cary 8454 UV-Vis spectrophotometer with UV-Vis ChemStation software.
• Cary 3500 UV-Vis spectrophotometer with multicell module and UV Workstation software.
• Research-grade double out-of-plane Littrow monochromators and xenon flash lamp light source (Cary 3500).

Key Results and Discussion

1. Wavelength Identification:

• Both instruments detected dichromate peaks at 257 nm and 350 nm, confirming expected values.

2. Calibration and Accuracy:

• Each instrument achieved R² = 0.9999 for a six-point calibration at 257 nm.
• Measured sample concentrations: 61.37 mg/L (Cary 8454) vs. 60.72 mg/L (Cary 3500) compared with a certified 60.73 mg/L.
• Cary 3500 exhibited smaller absorbance errors at high concentrations (>3 Abs), thanks to an extended photometric range up to 4 Abs.

3. Throughput and Timing:

1. Single-scan times: 7 s for Cary 8454; 92 s for Cary 3500 at 0.1 s averaging.
2. Calibration routine times: 141 s for Cary 8454; 92 s for Cary 3500.
3. Using 0.004 s averaging, the Cary 3500 further reduced measurement times, demonstrating rapid multicell acquisition.

Benefits and Practical Applications

The Cary 3500 offers several operational advantages over the Cary 8454:

• Simultaneous measurement of up to seven samples via a robust, non-moving multicell module reduces variability between standards and samples.
• Extended photometric range (to 4 Abs) eliminates the need for repeated dilutions of highly absorbing samples.
• Streamlined user workflow with updated software enhances method development and routine analysis.
• Optional compliance modules (21 CFR Part 11/EU Annex 11) support regulated laboratory environments.

Future Trends and Opportunities

As analytical demands grow, future UV-Vis spectrophotometers will likely integrate:

• Advanced automation for sample handling and data processing.
• Enhanced spectral bandwidth control and higher scan rates.
• Artificial intelligence-driven method optimization and anomaly detection.
• Greater connectivity for remote monitoring and cloud-based data management.

Conclusion

Both the Cary 8454 and Cary 3500 deliver high accuracy and reproducibility for potassium dichromate quantification. The Cary 3500’s multicell architecture, extended linear range, and modern software represent significant workflow enhancements, making it an effective successor for laboratories migrating from the Cary 8454 under GMP and GLP frameworks.

Reference

Agilent Technologies. Technical overview: Comparing the Performance of the Cary 3500 and Cary 8454 UV-Vis Spectrophotometers for Sample Quantification Measurements. 5994-1047EN, June 2019.